Visually impairing cataract, or clouding of the lens, is the leading cause of preventable blindness in the world. Presently, cataracts are treated by surgical removal of the affected lens and replacement with an artificial intraocular lens (“IOL”). FIG. 1 is a diagram of an eye 100 illustrating anatomical structures related to the surgical removal of a cataract and the implantation of an IOL. The eye 100 comprises an opacified lens 102, an optically clear cornea 104, and an iris 106. A lens capsule (capsular bag 108) located behind the iris 106 of the eye 100 contains the opacified lens 102. More particularly, the opacified lens 102 is seated between an anterior capsule segment (anterior capsule 110) and a posterior capsular segment (posterior capsule 112). The anterior capsule 110 and the posterior capsule 112 meet at an equatorial region 114 of the capsular bag 108. The eye 100 also comprises an anterior chamber 116 located in front of the iris 106 and a posterior chamber 118 located between the iris 106 and the capsular bag 108.
A common technique for cataract surgery is extracapsular cataract extraction (“ECCE”), which involves the creation of an incision near the outer edge of the cornea 104 and an opening in the anterior capsule 110 (i.e., an anterior capsulotomy) through which the opacified lens 102 is removed. The lens 102 can be removed by various known methods. One such method is phacoemulsification, in which ultrasonic energy is applied to the lens to break it into small pieces that are aspirated from the capsular bag 108. Thus, with the exception of the portion of the anterior capsule 110 that is removed in order to gain access to the lens 102, the capsular bag 108 may remain substantially intact throughout an ECCE. The intact posterior capsule 112 provides a support for the IOL and acts as a barrier to the vitreous humor within the posterior chamber 120 of the eye 100. Following removal of the opacified lens 102, an artificial IOL, which may be designed to mimic the transparency and refractive function of a healthy lens, is typically implanted within the capsular bag 108 through the opening in the anterior capsule 110. The IOL may be acted on by the zonular forces exerted by a ciliary body 122 and attached zonules 124 surrounding the periphery of the capsular bag 108. The ciliary body 122 and the zonules 124 anchor the capsular bag 108 in place and facilitate accommodation, the process by which the eye 100 changes optical power to maintain a clear focus on an image as its distance varies.
A frequent complication of ECCE and other forms of cataract surgery is opacification of the posterior capsule 112. Posterior capsule opacification (“PCO”) results from the migration of residual lens epithelial cells from the equatorial region 114 of the capsular bag 108 toward the center of the posterior capsule 112. One factor contributing to the development of PCO is contact between the IOL and the surface of the posterior capsule 112. Subsequent to ECCE, the lens epithelial cells may proliferate between the IOL and the surface of the posterior capsule 112, leading to wrinkling and clouding of the normally clear posterior capsule 112. If clouding of the posterior lens capsule 112 occurs within the visual axis, then the patient will experience a decrease in visual acuity and may require additional surgery to correct the patient's vision.
A widely utilized procedure to clear the visual axis of PCO is Neodymium: Yttrium-Aluminum-Garnet (“Nd/YAG”) laser capsulotomy, in which a laser beam is used to create an opening in the center of the cloudy posterior capsule 112. However, Nd/YAG laser capsulotomy exposes patients to the risk of severe complications that can lead to significant visual impairment or loss, such as retinal detachment, papillary block glaucoma, iris hemorrhage, uveitis/vitritis, and cystoid macula edema. Moreover, the laser energy is ordinarily directed though the IOL, which may damage the optics of the implant or disrupt its placement within the capsular bag 108. Accordingly, there exists a need to prevent the occurrence of PCO rather than treating PCO at a later date after implantation of an IOL.